1. Field of the Invention
The present invention relates to a multifunction MEMS element and a method to make the multifunction MEMS element. In particular, the present invention relates to a multifunction MEMS element and a method to integrate a MOS and a multifunction MEMS element.
2. Description of the Prior Art
A micro electro mechanical system (MEMS) is a tiny device with both the electronic and mechanical functions. Apart from the conventional electro and mechanical processing, the micro electro mechanical system installs some micro structures, such as a circuit, a sensor, an actuator, a cantilever, a beam, a membrane, a channel, a cavity, a joint, a hinge, a link, a crank, a gear or a rack on a Si wafer by miniaturization techniques and is operated based on, for example, electromagnetic, electrostrictive, thermoelectric, piezoelectric, or piezoresistive effects. The manufacture method of the micro electro mechanical system therefore requires various processing techniques.
The current methods to manufacture the micro electro mechanical system are, for example, the silicon-based method, the LIGA method and the polymer method. Considering the cost for the mass production, the well-developed semiconductor process, such as lithography, vapor deposition and etching is much favored to manufacture the micro electro mechanical system on the isolation layer or other substrates due to its potential capability.
On the other hand, an inductor is a passive electronic component that stores energy in the form of a magnetic field, and an inductor tends to resist any change in the amount of current flowing through it. The inductor is usually used with capacitors in various wireless communications applications for providing stable currents, switched phases, filtering and resonance. In its simplest form, the inductor consists of a wire loop or coil. The inductance is directly proportional to the number of turns, the thickness, the length, and the radius of the coil. The inductance also depends on the type of material around which the coil is wound. In a semiconductor manufacturing process, at least two metal layers with specifically designed layout patterns and a plurality of via plugs for connecting these two metal layers are used to form a wire loop, thus fabricating an inductor onto an integrated circuit chip. Recently, for obtaining an inductor with a smaller size, a three-dimensional inductor is produced to have an increased coil density. However, in order to form the inductor, much space on the substrate is occupied.
Because both the micro electro mechanical system and the MOS element may be manufactured by the techniques which are integrated with the current semiconductor technology, the manufacturing process which integrates the micro electro mechanical system and the MOS element becomes a hot issue. In order to form each part of the micro electro mechanical system, the metal interconnection process is employed to construct the components of the micro electro mechanical system. When the micro electro mechanical system has more and more parts, the method is getting more and more complicated and more and more space is needed to accommodate them.
Therefore, a novel method to integrate the micro electro mechanical system and the MOS element is needed. In one aspect, a single micro electro mechanical element may have multiple functions to save the space on the chip. In another aspect, two different methods to make the micro electro mechanical system and the MOS element are integrated to simplify the integration of the semiconductor process, lower the cost for manufacture and render the products to be much favorable.